Variable beam modulation

Abstract

The invention relates to a device (10) and to a method for simple introduction of a plurality of optical elements (18a-c) into a beam path, in particular into the beam path of an EUV-generation system. The device (10) preferably comprises a stepped pulley (32) that has at least one step designed to move the optical elements (18a-c) indirectly or directly into the beam path. More preferably, springs (36a-c) are provided, which indirectly or directly move the optical elements (18a-c) out of the beam path when the step(s) does / do not indirectly or directly act upon the optical elements (18a-c). The stepped pulley (32) can in particular be indirectly or directly rotated by a flexible shaft (28). Levers (34a-c) may be provided, each of which can be acted upon at one end by the step(s) and comprises at the other end the optical elements (18a-c). The strength of the optical effect of the optical elements (18a-c) increases with respect to an other of the optical elements (18a-c), preferably by the same factor, in particular by a factor of two.

Description

Background of the invention

[0001] The invention relates to a device and a method for beam modulation.

[0002] It is known to modulate the properties of a beam, especially a laser beam. This involves using optical elements that typically need to be installed and removed to change the beam modulation. However, this is cumbersome, time-consuming, and requires detailed expertise.

[0003] Furthermore, devices for beam modulation are known from the prior art in which optical elements can be moved in and out of a beam path by means of levers. Such devices are known, for example, from manufacturers such as Newport Corp. (OC1-FB Optical Filter Bank, https: / / web.archive.org / web / 20201021161143 / https: / / www.newport.com / p / OC1-FB) and Thorlabs (90° Flip Mounts, https: / / web.archive.org / web / 20201204112019 / https: / / www.thorlabs.de / newgrouppage9.cfm?objectgroup_id=1447). Object of the invention

[0004] It is an object of the invention to provide a device and a method for significantly simplified variable beam modulation. Description of the invention

[0005] This problem is solved according to the invention by a device according to claim 1 and a method according to claim 12. The dependent claims describe preferred embodiments.

[0006] The problem according to the invention is thus solved by a device for beam modulation, wherein the beam modulation is achieved by moving optical elements into and out of a beam path. The device comprises a first lever with a first optical element and a second lever with a second optical element. The device further comprises an actuating device. The actuating device is configured to move the first lever and the second lever. This allows the first optical element and the second optical element to be moved into and out of the beam path. In addition, the actuating device comprises a stepped disk, wherein the levers can be moved by means of steps on the stepped disk.

[0007] The time-consuming installation and removal of optical elements is avoided. The time required to change over the device can be reduced to less than 5%. The first optical element is preferably arranged or formed in an optical housing of the first lever. The second optical element is preferably arranged or formed in an optical housing of the second lever.

[0008] To better modulate the beam characteristics, the device can include a third lever with a third optical element. In this case, the actuating mechanism can be configured to move the third optical element into and out of the beam path. In other words, the device can be configured to insert and remove the first, second, and third optical elements into and out of the beam path without requiring complex installation and removal procedures. The third optical element is preferably arranged or formed within an optical housing of the third lever.

[0009] Preferably, several levers, in particular all levers, are mounted with an axis of the device held at both ends.

[0010] The steps can be arranged on the stepped disk or – preferably – formed integrally with the stepped disk. The stepped disk or cam disk represents a structurally simple mechanical device for moving the levers. Preferably, the levers are pivotable by means of steps on the stepped disk. The steps of the stepped disk are preferably arranged on the end face – and not along the circumferential surface (as in a gear ring) of the stepped disk. Each lever can have one, in particular long, lever arm with the optical element and one, in particular short, lever arm, wherein the one, in particular short, lever arm can be actuated by the steps or cams to pivot the levers about a pivot point.

[0011] The stepped disc is preferably mounted to rotate about its main axis. According to the invention, "rotatable" also includes pivoting movements of less than 360°.

[0012] The levers are preferably movable by means of radially offset steps on the stepped disc. This allows the levers to be actuated independently of each other.

[0013] Alternatively or additionally, several steps can be offset by a certain amount, so that at least with a partial rotation of the stepped disk, only one optical element is exchanged. This achieves a particularly uniform load when the actuating device is operated. Alternatively or additionally, the steps on the stepped disk can also be offset by such an amount that with a partial rotation of the stepped disk, two or more optical elements are exchanged simultaneously. In this way, two or more optical elements can be introduced into the beam path with particular efficiency.

[0014] The steps can be arranged or designed in such a way that the levers can perform the following movements in succession: a) Replace the first optical element in the beam path; b) replace the first optical element out of the beam path and replace the second optical element; c) replace the first optical element.

[0015] The movements can preferably be performed as pivoting movements.

[0016] In the case of at least three levers, the stages can be arranged or designed such that the third optical element is replaced in the aforementioned steps a) to c) and the levers can perform the following movements after movements a) to c): d) Replace the first optical element, replace the second optical element and replace the third optical element; e) Replace the first optical element; f) Replace the first optical element and replace the second optical element; g) Replace the first optical element.

[0017] The movements can preferably be performed as pivoting movements.

[0018] Before process step a) and / or after process step g), the optical elements can be interchangeable from the beam path, in particular by designing / arranging no stage.

[0019] The device can have one or more springs to move the optical elements into a predefined position when they are replaced or moved out of position.

[0020] A structurally simple implementation of the invention is achieved if the adjusting device has a spur gear reduction and the stepped disc can be driven by the spur gear reduction of the adjusting device.

[0021] The device can have a flexible shaft. The flexible shaft allows for flexible positioning of the adjusting mechanism.

[0022] The optical elements are preferably identical except for the strength of their optical effect. The strength of the optical effect of each optical element preferably increases by a factor of one, and in particular by a factor of two, with respect to each other optical element.

[0023] In a particularly preferred embodiment of the device, each optical element comprises an absorber. More preferably, each optical element is designed in the form of an absorber. The absorbers are preferably plate-shaped. Particularly preferably, the second optical element has twice the thickness of the first optical element. More preferably, the third optical element has twice the thickness of the second optical element.

[0024] According to the aforementioned steps a) to c), a single absorber thickness, followed by a double absorber thickness, followed by a triple absorber thickness, is then introduced or exchanged in the beam path. In other words, the absorption is increased stepwise.

[0025] According to the aforementioned steps d) to g), a four-fold absorber thickness, followed by a five-fold absorber thickness, followed by a six-fold absorber thickness, followed by a seven-fold absorber thickness is then moved into the beam path.

[0026] Preferably, the absorbers each comprise a CaF₂ plate. Particularly preferably, the absorbers are each formed in the form of a CaF₂ plate.

[0027] The device preferably includes a laser for generating a beam propagating along the beam path, i.e., a beam in the form of a laser beam. Preferably, the laser is configured to emit an infrared (IR) laser beam. The laser may be configured as a CO₂ laser.

[0028] The device can include a detector for measuring the beam properties of the beam traveling in the beam path. The detector is preferably in the form of a photoelectromagnetic (PEM) detector.

[0029] The device preferably includes an extreme ultraviolet (EUV) light generation unit. The EUV generation unit comprises the aforementioned laser for generating the beam traveling along the beam path. The beam generated by the laser is preferably amplified by one or more amplifier lasers and preferably directed onto a tin droplet that can be produced in the EUV generation unit ("EUV system"). A plasma can then be generated in the tin droplet, which emits the EUV radiation.

[0030] The problem according to the invention is further solved by a method for beam modulation with a device described herein. The device has at least two levers, each having an optical element, wherein the levers successively perform the following movements: a) Replace the first optical element in the beam path; b) replace the first optical element out of the beam path and replace the second optical element; c) replace the first optical element.

[0031] The lever movements are preferably performed as pivoting movements.

[0032] The device can have at least one third lever with a third optical element, wherein the third optical element is moved out during process steps a) to c) and the process comprises the following further process steps: d) Replace the first optical element, replace the second optical element and replace the third optical element; e) Replace the first optical element; f) Replace the first optical element and replace the second optical element; g) Replace the first optical element.

[0033] The movements are preferably performed as pivoting movements.

[0034] Before process step a) and / or after process step g), the optical elements can be removed from the beam path, in particular by eliminating any step (total thickness of optical elements zero). Further advantages of the invention will become apparent from the description and the drawing.

[0035] The embodiments shown and described are not to be understood as an exhaustive list, but rather as examples for the description of the invention. Detailed description of the invention and drawing

[0036] Fig. 1 shows an isometric view of a beam modulation device according to the invention. Fig. 2 shows another view of the device with the cover removed. Fig. 3 shows a partially cutaway view of the device, showing plate-shaped optical elements mounted in levers. Fig. 4 shows another view of the device, showing the actuation of the levers by a stepped disk. Fig. 5 shows a side view of the device, further illustrating the actuation of the levers by the steps of the stepped disk. Fig. 6 shows a view of the stepped disk to illustrate the steps.

[0037] Fig. 1 shows a device 10 for modulating a beam 12, Here in the form of a laser beam. Beam 12 is used to generate EUV radiation by an EUV (extreme ultraviolet light) generation system. 14.The EUV radiation is generated by bombarding a tin droplet (not shown) with beam 12. In the Fig. 1 In the part of the device 10 shown, the beam 12 is not directed at the tin droplet, but is at least partially coupled out for its characterization and placed in a detector. 16 analyzed. The detector 16 is preferably designed in the form of a photoelectromagnetic (PEM) detector.

[0038] Since the beam 12 would damage the detector 16 due to its high power, optical elements are 18a, 18b, 18c (more visible in Fig. 3 ), here in the form of absorbers. The optical elements 18a-c can be arranged in a beam path as needed. 20 of the beam 12. A positioning device is required for inserting and removing the optical elements 18a-c. 22 planned.

[0039] The actuating device 22 can be operated manually and / or by an actuator (not shown), for example an electric motor. In this case, tool intervention is required. 24 A tool (not shown) is provided for manually operating the adjusting device 22. A tool, preferably in the form of a multi-sided wrench, can preferably be inserted into the tool engagement 24.

[0040] Fig. 2 The device 10 shows a cover 26 was removed. Fig. 2 It is evident that the tool engagement 24 is actuated via a shaft, which is flexible in this case. 28 This can be done. The flexible shaft 28 allows for flexible positioning and actuation of the tool engagement 24.

[0041] The rotation of shaft 28 is controlled via a spur gear reduction. 30 on a stepped disc 32The actuating device 22 can be transferred. The stepped disc 32 serves to move, in particular pivot, levers. 34a, 34b, 34c in beam path 20 (see Fig. 1 The levers 34a-c feature the optical elements 18a-c.

[0042] If the levers 34a-c are not actuated by the stepped disc 32, they are held in place by springs. 36a, 36b, 36c from beam path 20 (see Fig. 1 ) moves. Springs 36a-c are attached at one end to hooks. 38a, 38b, 38c the lever 34a-c is engaged. In Fig. 2 The insertion of the springs 36a-c into the hooks 38a-c is not shown for illustrative purposes. On the other hand, the springs 36a-c are attached to a holder. 40 arranged.

[0043] Fig. 3 The device 10 is shown in a partially cutaway view. From Fig. 3It is evident that the optical elements 18a-c are received or mounted in the levers 34a-c. The optical elements 18a-c are designed in the form of absorbers, particularly plate-shaped ones. In this case, the optical elements 18a-c are designed in the form of CaF₂ plates. The optical element 18b has twice the thickness of the optical element 18a. The optical element 18c has twice the thickness of the optical element 18b. Depending on the combination of the inserted optical elements 18a-c, the addition of the absorption of the optical elements 18a-c results in a total absorber with one, two, three, four, five, six, or seven times the thickness of the optical element 18a.

[0044] Fig. 4 The device 10 shows, wherein from Fig. 4 It is evident that the levers 34a-c are on an axis, in particular a common one. 42The axle 42 is preferably mounted at both ends on the bracket 40. The levers 34a-c each have a long lever arm with the optical element 18a-c and a short lever arm. The short lever arm is supported by steps. 44 the stepped disk 32 is actuated. The steps 44 are preferably formed integrally with the stepped disk 32. By rotating the stepped disk 32, the steps 44 press against the, in particular short, lever arms of the levers 34a-c in order to deflect the levers 34a-c and thereby move the optical elements 18a-c into the beam path 20 (see Fig. 1 ) to move, in particular to swivel.

[0045] Fig. 5 The device 10 is shown in a side view. From Fig. 5It is evident that the levers 34a-c are arranged radially offset from each other on the stepped disk 32. Depending on the arrangement and design of the steps 44, the levers 34a-c can therefore be actuated independently of each other by the stepped disk 32.

[0046] Fig. 6 Figure 3 shows the stepped disk 32 in a top view. Dashed lines indicate the actuation of the levers 34a-c, with lever 34a being actuated radially outwards, lever 34b radially inwards, and lever 34c radially inwards (see Figure 3). Fig. 5 ). From a synthesis of the Fig. 5 with the Fig. 3 It becomes clear that when the stepped disk 32 is rotated, the following levers 34a-c or optical elements 18a-c are actuated in order to achieve the following total strength of the optical elements 18a-c in the beam path 20 (see Fig. 1 to contribute: Procedure step Move optical elements Move optical elements Optical elements in the beam path Total thickness of the optical elements in the beam path in thickness(es) of the optical element 18a a) 18a 18a 1 b) 18b 18a 18b 2 c) 18a 18a, b 3 d) 18c 18a, b 18c 4 e) 18a 18a, c 5 f) 18b 18a 18b, c 6 g) 18a 18a, b, c 7

[0047] The stepped disk 32 allows the total power of the optical elements 18a-c to be increased linearly in steps.

[0048] Before process step a) and / or after process step g), the optical elements 18a-c can be removed from the beam path 20 (see Fig. 1 ), in particular by training / arranging no level 44, removed (total strength zero optical elements).

[0049] Preferably, as in the present embodiment, only one optical element 18a-c is placed in the beam path 20 during the rotation of the stepped disk 32 (see Fig. 1 ) moves. The movement is effected by the springs 36a-c when the levers 34a-c are unactuated.

[0050] Based on a combined view of all figures in the drawing, the invention relates to a device 10 and a method for easily inserting several optical elements 18a-c into a beam path 20, in particular into the beam path 20 of an EUV generating plant 14. According to the invention, the device 10 has a stepped disk 32 with steps 44, which are configured to move the optical elements 18a-c directly or indirectly into the beam path 20. Preferably, springs 36a-c are provided which move the optical elements 18a-c directly or indirectly out of the beam path 20 when there is no direct or indirect actuation of the optical elements 18a-c by the step(s) 44. The stepped disk 32 is rotatable, in particular directly or indirectly, by a flexible shaft 28. Levers 34a-c are provided, each of which can be actuated at one end by the steps 44 and can have the optical elements 18a-c at the other end.The strength of the optical effect of the optical elements 18a-c increases with respect to each other of the optical elements 18a-c preferably by the same factor, in particular by a factor of two. Reference symbol list

[0051] 10 Device 12 Beam 14 EUV generating unit 16 Detector 18a-c Optical element 20 Beam path 22 Actuating device 24 Tool engagement 26 Cover 28 Shaft 30 Spur gear reduction 32 Stepped disc 34a-c Lever 36a-c Spring 38a-c Hook 40 Bracket 42 Axis 44 Step

Claims

1. A device (10) for beam modulation by inward and outward moving of optical elements (18a-c) into and out of a beam path (20), wherein the device (10) comprises the following: - a first lever (34a-c) with a first optical element (18a-c); - a second lever (34a-c) with a second optical element (18a-c); - an adjusting apparatus (22) for moving the first lever (34a-c) in order to move the first optical element (18a-c) into the beam path (20) and out of the beam path (20), and to move the second lever (34a-c) in order to move the second optical element (18a-c) into the beam path (20) and out of the beam path (20), characterized in that the adjusting apparatus (22) comprises a stepped disc (32), wherein the levers (34a-c) are movable through steps (44) of the stepped disc (32).

2. The device according to claim 1, in which the device (10) comprises a third lever (34a-c) with a third optical element (18a-c), wherein the adjusting apparatus (22) is designed to move the third lever (34a-c) in order to move the third optical element (18a-c) into the beam path (20) and out of the beam path (20).

3. The device according to claim 1 or 2, in which each of the levers is movable through radially offset steps (44) on the stepped disc (32).

4. The device according to one of the preceding claims, in which a plurality of steps (44) are offset circumferentially so that, at least when the stepped disc (32) is rotated sectionally, only one optical element (18a-c) is moved into the beam path (20).

5. The device according to claim 4, in which the steps (44) are arranged or designed such that the levers (34a-c) with the optical elements (18a-c) can carry out the following movements in succession: a) moving the first optical element (18a-c) into the beam path (20); b) moving the first optical element (18a-c) out of the beam path (20) and moving the second optical element (18a-c) in; c) moving the first optical element (18a-c) in.

6. The device according to claim 5 in connection with claim 2, in which the steps (44) are arranged or designed such that in the case of the movements a) to c), the third optical element (18a-c) is moved out and the levers with the optical elements (18a-c) can carry out the following movements in succession: d) moving the first optical element (18a-c) out, moving the second optical element (18a-c) out and moving the third optical element (18a-c) in; e) moving the first optical element (18a-c) in; f) moving the first optical element (18a-c) out and moving the second optical element (18a-c) in; g) moving the first optical element (18a-c) in.

7. The device according to any of the preceding claims, in which the device (10) comprises one or more springs (36-c) for moving the levers (34a-c) to a predefined position when they are in the state of not being acted upon by the adjusting apparatus (22).

8. The device according to any of the preceding claims, wherein the adjusting apparatus comprises a spur gear reduction (30), and wherein the stepped disc (32) can be driven by the spur gear reduction (30) of the adjusting apparatus (22).

9. The device according to any of the preceding claims, in which the adjusting apparatus (22) comprises a bendable shaft (28).

10. The device according to any of the preceding claims, in which each of the optical elements (18a-c) comprises an absorber.

11. The device according to claim 11 in which each of the absorbers comprises a CaF2 plate.

12. A method for modulating a beam (12) with a device (10) according to any of the preceding claims, wherein the device (10) comprises at least two levers (34a-c), each of which comprises an optical element (18a-c), and the method comprises the following method steps in succession: a) moving the first optical element (18a-c) into the beam path (20); b) moving the first optical element (18a-c) out of the beam path (20) and moving the second optical element (18a-c) in; c) moving the first optical element (18a-c) in.

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